How to Apply Polyurethane
Getting a smooth, smudge-free finish with oil-based polyurethane is within your reach by following the steps in this article. The oil-based polyurethane varnish enhances the natural beauty and texture of the wood. Our 8-step approach shows you how to apply the varnish successfully. A good quality natural bristle brush, a reasonably dust-free and well-ventilated space, and a little patience are all you need.
Finish off your woodworking project or furniture repair job with an oil-based polyurethane varnish to bring out the natural beauty and texture of the wood. Learn how to prepare your wood surface and successfully apply a perfect finish with these detailed steps.
- sanding block
- shop vacuum
- Automotive polishing compound
- Automotive friction compound
- lint-free cloth
- Mineral spirits
- Oil-based polyurethane
- tack cloth
- wet/dry sandpaper
We use an oil-based polyurethane finish, although you can also use water-based urethane finishes to great effect. But the color and depth you get is no match for oil-based urethanes. If you choose a water-based product, the process for obtaining a smooth finish is basically the same. Just be sure to use a dust-proof cloth that is suitable for water-based finishes, such as gauze moistened with denatured alcohol.
Step 1: sand the surface
- Sand your project with increasingly fine sandpaper grits.
Note: Paper with a higher grain number removes the deeper scratches left by paper with a lower grain number.
Pro Tip: Most projects need an initial sanding with a medium sandpaper (100 grit) followed by a fine sandpaper (150 grit) and then superfine sandpaper with 220 grit.
Step 2: remove the dust
- Once the wood is free of stains, remove the dust.
Pro Tip: Use a vacuum cleaner with a soft brush, followed by a clean, lint-free cloth moistened with mineral spirits.
- As the last dust cleaning step, wipe the surface with an adhesive cloth.
Step 3: seal the surface
- Thin oil-based polyurethane with two parts polyurethane and one part mineral spirits.
Pro Tip: Pour the products into a glass jar and gently stir the mixture with a stirring rod.
- Brush the sealer with a natural bristle brush in long, even strokes. Make sure you catch all the runs.
Note: Some stains seal on their own. See the can for this information. If the stain is self-sealing, you can skip this step.
Pro tip: never shake a polyurethane can! You will introduce air bubbles into the mixture that will end up as bumps on the finished surface.
Pro Tip: Use a good quality natural bristle brush to apply oil-based polyurethane. Synthetic Blast Tip Brushes (with each strand divided into multiple strands at the tip) can introduce air bubbles into the finish.
- Load your brush by dipping it about 1 inch into the mixture and brush the wood with long, even strokes from edge to edge.
- Maintain an overlapping wet edge with each pass until the surface is completely covered.
- Collect all the drops with your brush and apply them on the surface.
Step 4: Apply the first layer of polyurethane
- Within 24 hours of applying topcoat, apply topcoat directly from can.
Pro Tip: Avoid rubbing the brush over the rim of the can, as this can cause air bubbles.
- Spread the varnish over the entire surface in long, even strokes.
Pro tip: don't use too much or it's likely to leak; use just enough to get a nice even coat with no dry spots. Once the surface is covered, rebrush with the grain, end to end.
- Overlap your strokes to get an even layer.
- Capture all drops, especially at the lower edges.
Step 5: remove the bumps
When the surface is completely dry to the touch (at least 12 hours), cut off any drops with a razor blade.
Pro Tip: Make sure you don't cut below the surrounding surface.
Step 6: Wet Sand the First Coat
- After the primer has dried for 24 hours, remove small spots by wet sanding with 400-grit sandpaper mounted to a sandpaper block.
- Dip the sandpaper in the water and use circular motions to remove any stains and dust.
Pro Tip: Use enough water to lubricate the sandpaper so you don't burn the delicate finish. Sand just enough to remove the stain.
- When the surface is smooth, wipe it with a damp cloth and dry it with a clean, dust-free cloth.
Apply the second coat
- 24-48 hours after applying the first coat, apply the second and last coat using the same procedure as the first coat.
Step 7: Repeat steps 5 and 6 if necessary
- Once the second coat is dry, scrape off any bumps (per Step 5) and sand the surface with damp sandpaper (per Step 6).
Note: Follow these steps only if absolutely necessary. If you have to sand the second coat, you will need to polish the surface.
Step 8: Buff the surface if you sand the second coat
- Wait at least 48 hours and then buff the finish with an auto scrubbing compound.
- Dampen a clean cotton cloth with water and apply an automotive friction compound to the surface in a circular motion.
Note: The compound has a fine abrasive that removes any scratches left by the 400-grit sandpaper and restores the gloss to the polyurethane finish.
- After scrubbing, allow the surface to dry and buff the finish with a clean, dry cloth.
Pro Tip: If the finish is still a bit hazy, apply more car polishing compounds using the same method. Allow to dry and then buff the surface.
Pro Tip: For an even higher shine, apply a polishing compound as a final step.
We hope you enjoy watching this video about Tips to Apply Polyurethane Like a Pro
Source: Live Free
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